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Energy question of the week: What makes a power grid intelligent?

A closely-interconnected grid of power lines and wires 1.7 million kilometres in length and running from power stations to wall sockets delivers a reliable power supply throughout Germany. It has evolved and been maintained over decades, extended in leaps and bounds, and virtually no-one gives any real thought to the interplay between generator and consumer, power frequency and high voltages, sub-stations and transformers. Now, in response to the rising proportion of electricity generated from renewable sources, the term Smart Grid (the 'intelligent' power grid) is now coming into common parlance. Was, and is, our existing power grid really so 'dumb'?

The way out of the dead end

Despite all the control centres operated by the four major and a few smaller power-generating companies in our country, the performance capability of our power grid is limited. This is due to the fact that, in the early days, the grid was designed exclusively to distribute power from central power stations to individual consumers. It is essentially a ‘one-way street’, and one that is increasingly being tested to its limits. On a decentralised or 'remote' basis, smaller power-generating companies are contributing to the national grid. They may employ a generator powered by biogas, or a small hydroelectric power station. Wind farms, with their occasional sharp fluctuations in yield, are also being added to the mix. As a consequence, existing technology is finding it increasingly difficult to manage the power grid. If, as planned, the proportion of power generated from renewable sources is to continue rising, it is essential to expand and modify our national power grid.

"The intelligent power grid is prerequisite for reliable power supply in the future." Credit: dpa.

This trend affects all industrialised nations to a similar degree; it is not a problem that Germany faces alone. Forecasts suggest that investments amounting to several hundred billion euro are being planned for the next two decades – a gigantic market in which German companies want to secure themselves a large share. Many technologies – first and foremost the linking of the power grid to a data network – will be called upon to accomplish this objective, because this paradigm shift will have an impact at all levels – from high-voltage power lines carrying 400 kilovolts right through to the domestic 230 volt power socket in the home.

Many ideas for a single goal

In the home, intelligent electricity meters will monitor the amount of power delivered and used for domestic purposes. As weather data become more reliable, the power yield from wind and solar power will become easier to forecast with some degree of accuracy. At a local level, different smaller power-generating companies will be able to combine forces efficiently in what are known as 'virtual power stations', thereby making the entire grid easier to manage and control. Last but not least, the need for intermediate storage of electricity is rising – irrespective of whether it is done by fleets of electric cars, with their lithium-ion batteries, or using giant subterranean compressed air reservoirs. This is because the power grid is only able to transmit electricity, not store it.

In addition, DC power transmission lines carrying up to 800 kilovolts will be used to link all the sub-networks within Europe, to deliver a reliable transport system for power generating companies located far from where their output is actually used. "The intelligent power grid is absolutely essential for any safe and reliable power supply in the future. At present, DLR is working on appropriate solutions for the integration of renewable sources. A balanced mix of energy sources and a high-performance distribution network help to ensure that the electrical load demand is covered at all times and that the requirement for storage capacity is kept to a minimum," states Franz Trieb, from the DLR Institute of Technical Thermodynamics in Stuttgart. In later posts of the 'Energy Question of the Week', this blog will present exciting details of these ideas and proposed solutions.

The DLR Energy question of the week in 'The future of energy' Year of Science

The Federal Ministry of Education and Research (BMBF) has given the Year of Science 2010 the motto 'The future of energy'. For this reason the science journalist Jan Oliver Löfken will this year answer a question on the subject of energy in his blog each week. Do you have a question about how our energy supply might look in the future? Or do you want to know, for example, how a wave power plant works and how it can efficiently generate electricity? Then send us your question by email. Science journalist Jan Oliver Löfken will investigate the answers and publish them each week in this blog.

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Energy journalist Jan Oliver Löfken writes among other things, for the Technologie Review, Wissenschaft aktuell, Tagesspiegel, Berliner Zeitung and P.M. Magazin on issues involving energy research and industry. For DLR, he answered the Energy question of the week during the Year of Energy 2010.
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